Conventionally, there is known an unmanned running system for running a vehicle such as a dump truck without a driver in a working site such as a mine.
Referring to FIG. 9, there is shown an explanatory diagram of an unmanned running system according to a prior art. In this diagram, the unmanned running system has a plurality of vehicles 1 and a central monitor station 2 for monitoring operations of the plurality of vehicles 1.
The central monitor station 2 is arranged in a predetermined position in a working site and an observer is resident in the inside the central monitor station. The vehicle 1 has a position detecting unit (not shown) for detecting the current position to run without a driver in a predetermined course 3 under a supervision of the central monitor station 2 while communicating therewith wirelessly.
The vehicles 1 has an obstacle detecting unit 5 for detecting an obstacle 4 in the course 3.
The obstacle detecting unit 5 comprises a transmitter for emitting transmitted waves 29 such as electric waves or laser beams in a running direction and a receiver for receiving reflected waves 33, that is, the transmitted waves 29 which have returned to the vehicle after being reflected on the obstacle 4. By comparing the transmitted waves 29 with the reflected waves 33, it is detected whether or not there is any obstacle 4 in the course 3 in which the vehicle 1 is running in addition to a detection of a distance from the vehicle 1 to the obstacle 4.
The obstacle detecting unit 5 stops the vehicle 1 to prevent the vehicle 1 from colliding with the obstacle 4 if it recognizes the obstacle as one blocking the advance of the vehicle 1 such as a man, another vehicle 1, or a load which has dropped out of another vehicle 1. Then, a worker goes to the stopped place and removes the obstacle 4 before starting the vehicle 1.
The prior art, however, has problems below.
In other words, the obstacle detecting unit 5 sometimes stops the vehicle 1 recognizing a recess or projecting portion or an upward slope as the obstacle 4 by mistake in the course 3 in which the vehicle 1 is running.
Referring to FIG. 10, there is shown an explanatory diagram viewed from a lateral angle of the vehicle 1 running without a driver in the course 3. In this diagram, if the vehicle 1 is running in the even plane course 3 like a point A, it is possible to sense precisely whether or not there is an obstacle 4. If this vehicle 1 has approached an upward slope 6 like a point B, transmitted waves 29 are reflected on the upward slope 6 ahead of the vehicle 1 and the obstacle detecting unit 5 may recognize this upward slope 6 as an obstacle 4 by mistake.
In addition, the vehicle 1 causes pitching when running in the course 3 having recess or projecting portions like a point C, by which transmitted waves 29 are emitted downward and reflected on the ground, and it may recognize the ground as an obstacle 4 by mistake. The vehicle 1 is frequently stopped by this error recognition, and therefore there is a problem that a working efficiency of the unmanned running system is lowered.
Furthermore, it is hard for the obstacle detecting unit 5 to judge a size, materials and the like of the obstacle 4 (hereinafter, referred to as "true characters of the obstacle 4"). Therefore when the obstacle detecting unit 5 detects an obstacle 4, a worker always needs to go to a position of the stopped vehicle 1, independently of whether or not the obstacle is correctly recognized. Then, the worker determines whether or not the detected obstacle 4 blocks the advance of the vehicle 1 or whether or not the vehicle can run directly. If the vehicle 1 can run directly, it is restarted. In this manner, a lot of time is required to restart the vehicle 1, and therefore there is a problem that a working efficiency of the unmanned running system is lowered.